Means for reducing back pressure in silencers



Dec. 24, 1946. ys w cz 2,413,086

MEANS FOR REDUCING BACK PRESSURE IN SILENCERS Filed Jan. 10, 1945 20 Z2 M x l1 l! //V INVENTOR Jaw/v A Warm Kg BY c l/ .11452 ATTORNEYS Patented Dec. 24, 1946 MEANS FOR REDUCING BACK PRESSURE IN SILENCERS John P. Tyskewicz, Hartford, 001111., assignor to The Maxim Silencer Company, Hartford, Conn., a corporation of Connecticut Application January10, 1945, Serial No. 572,129

4 Claims. 1

The present invention pertains to devices for silencing the exhaust noise of internal combus-- tion engines and the like, and at the same time removing from the exhaust gases entrained dirt, sparks and the like.

More particularly the present invention relates to an improvement in the construction and arrangement of the outlet portions of such devices whereby the back pressure is materially reduced over present structures.

In one form of exhaust silencers and cleaners it is customary to so introduce the gases from the silencing chamber into the dirt separating chamber as to impart a whirling motion to the gases whereby the solid material is thrown by centrifugal force to the sides of the whirl chamber where it is collected. It has been common practice to provide the inner end of the conduit through which the gases are discharged with a conical mouth for funneling the whirling gases into the discharge conduit. Such an arrangement is shown in the patent to Roland B. Bourne 2,265,343 issued December 9, 1941. The vortex created at the small end of the discharge cone tends to create a back pressure and in the Bourne patent it is proposed to reduce this back pressure by providing one or more longitudinally disposed vanes extending from the large to the small end of the cone.

While there is an effective reduction of back pressure by the use of vanes in the cone as proposed by Bourne a substantial degree of back pressure is present and it is the object of this invention to secure a further and substantial reduction in the back pressure at the entrance to the discharge conduit.

In the accompanying drawing the present inv vention is disclosed embodied in a spark arrester silencer of the same type as is shown in the above mentioned Bourne patent.

In the accompanying drawing:

Fig. 1 is a side view of the device, partly broken away; and

Fig. 2 is a fragmentary perspective view showing the interior arrangement of the discharge cone.

Referring to the drawing the spark arrester is shown as generally comprising a cylindrical casing l having an inlet header H and an outlet header l2.

A transverse partition I3 divides the casing into a silencing chamber I4 and a whirl chamber I5. The discharge gases enter the chamber l4 through a conduit l6 and are introduced from chamber Hi to chamber l through silencing con:-

duits I! which open to chamber 15 at an angle to impart a whirling motion to the gases. Sparks, dirt, etc., thrown outwardly to the smooth wall of the chamber l5 are collected in a dirt collecting tube [8, through openings 19 formed in the wall l0, and fall into a dirt box 26 at the lower end of the tube. The discharge conduit 2| is provided with the conical section 22 having its small end connected to the inner end of the outlet conduit.

I have discovered that a marked reduction in back pressure may be secured by replacing the deep, curved vanes of the Bourne patent with one or more relatively shallow crossed interrupter bars 23, preferably positioned at the large end of the conical section. The depth of the interrupter bars 23 may vary but in any event an unpartitioned and uninterrupted space 24 of substantial axial depth is provided between the interrupters and the small end of the conical section. Preferably one half to three quarters of the axial depth of the conical section is unpartitioned and open from side to side, the remaining half, or one-quarter, being occupied by the interrupter bars. Approximately within the proportions mentioned the depth of the bars is not critical.

Preferably two interrupter bars are used as shown but in some instances the use of three secures slightly better results. For bars of a given depth the effectiveness in reducing back pressure decreases as they are disposed farther along the axis of the conical section toward its small end. Preferably the bars are therefore placed at or closely adjacent the large end of the conical section. Preferably also for usual conditions the conical member is so constructed that the angle between the surface elements of the conical member and the axis thereof is between thirty and sixty degrees and the slant height of the conical member is preferably made approximately equal to, or slightly less than, the diameter of the small end of the conical member.

The action of the interrupter bars appears to be one of breaking up the whirl of the exhaust gases as they leave the whirl chamber. The centrifugal forces tend to keep the gases whirling in the region, adjacent the walls of the chamber. Work is necessary to break up this action. The breaking up of the whirling action causes turbulence and the shallow interrupter bars represent the best compromise between induced turbulence losses incurred by the presence of the bars, balanced against the work necessary in extracting the whirling gases from the whirl chamber.

The principles of the invention are of course not limited to the particular form of spark-arrester silencer described but may be equally well applied to any device of the class having a conical outlet member.

I claim:

1. In a spark arrester silencer having a whirl chamber'and a gas outlet connection including a substantially imperforate open-ended conical member projecting into the whirl chamber, and one or more interrupter bars positioned within the large end of the conical member, a portion of the conical member of substantial axial depth between the interrupter and the small end of the conical member being unobstructed.

2. In a spark arrester silencer having a Whirl chamber and a gas outlet connection including a substantially imperforate open-ended conical member projecting into the whirl chamber, and one or more shallow interrupter bars positioned at thev large end of the conical member and extending inwardly towardthe small end of said member, theconical member for at least half of its depth being unobstructed.

chamber and a, gas outlet connection including 3. In a spark arrester silencer having a whirl chamber and a gas outlet connection including a substantially imperforate open-ended conical member projecting into the whirl chamber, and one or more interrupter bars positioned in said conical member and occupying between onequarter and one-half of the axial depth of the member, the remainder of the member being unobstructed.

4. In a spark arrester silencer having a whirl a substantially imperforate open-ended conical member projecting into the whirl chamber, a pair of crossed interrupter bars positioned in said conical member and occupying between onequarter and one-half of the axial depth of the member; the remainder of the member being unobstructed, the slant height of the conical member approximating the diameter of the small end of the member and the surface elements of the conical member making an angle of between thirty and sixty degrees with the axis thereof. JOHN P. 'IYSKEWICZ 

